Conventional automotive power supply systems include a voltage regulator, an engine-driven alternator and a battery. The voltage regulator serves to maintain the output voltage of the alternator in accordance with the voltage requirements of the battery by controlling the current flow through the field windings of the alternator.
One problem associated with conventional system power supply systems results from large system load current variations. Such variations might occur when the vehicle's climate control system is activated. This increased electrical load quickly reduces the output voltage of the alternator, causing the voltage regulator to increase the field current applied to the alternator. This increase in field current suddenly loads the alternator, which in turn increases the load on the engine and the vehicle speed slows dramatically.
If a speed control system is being operated concurrently, the speed control system increases engine speed. Typically, the air conditioning clutch is then deenergized to allow for increased engine performance until the preset vehicle speed is attained. When the preset speed is attained, the air conditioning clutch is again energized, and the cycle repeats. It is desirable, therefore, to prevent this condition by controlling the alternator response to system load current variations.
U.S. Pat. No. 3,373,333, issued to Eckard, discloses a voltage and current regulator for an automotive electrical system. The system is capable of keeping the battery charged to a desired extent and supplying sufficient current to operate several electrical current consuming mechanisms without the possibility of overcharging the battery.
U.S. Pat. No. 3,544,881, issued to Raver et al., discloses a transistor voltage and current regulating system for an alternating current generator. The system controls the generator voltage in accordance with changes in generator load current utilizing an output transistor which is controlled by a first driver transistor responsive to voltage and a second driver transistor responsive to current developed by the generator.
U.S. Pat. No. 4,308,492, issued to Mori et al., discloses a method of charging a vehicle battery utilizing an electronically controlled data processing device, such as a microcomputer. The method controls battery charging conditions in accordance with temperature, battery electrolyte, external electric loads and battery voltage, so as to prevent voltage drop due to overloading and to insure stable battery charging.
U.S. Pat. No. 4,459,489, issued to Kirk et al., discloses a generator load response control. The load response control prevents the imposition of a sharply increased torque load on the engine when an electrical is applied to the generator. The load control detects a sudden drop in generator output voltage and gradually increases the field current from a level substantially equal to the field current that existed just prior to the detected voltage drop.
U.S. Pat. No. 4,543,521, issued to Morishita et al., discloses a c control microcomputer device for a vehicle. The microcomputer determines the most suitable reference voltage for the charging system voltage regulator based on various input data from the charging system and an engine control microcomputer. The device is also useful for preventing the overcharging or over-discharging of the battery through a fault detection mechanism.
U.S. Pat. No. 4,629,968, issued to Butts et al., discloses a load control system for controlling a field current of an alternating current generator and the idle speed control system for the engine that drives the generator. The system operates such that when a large electrical load is applied to the generator, the system senses a drop in generator output voltage and then maintains the idle speed control system of the engine in such a manner as to increase the fuel-air mixture supplied to the engine in anticipation of the fact that field current will be increased due to the application of the electrical load.
U.S. Pat. No. 4,659,977, issued to Kissel et al., discloses a microcomputer controlled electronic alternator for vehicles. The microcomputer utilizes a battery temperature signal to calculate a desired set point voltage based on inverse first-order relationship between battery temperature and desired battery voltage. Current is supplied to the alternator field windings in accordance with a between the desired set point voltage and the battery voltage signal in response to a control signal from the microcomputer. The microcomputer is also provided with additional feedback information relating to various driving conditions such as throttle position and engine RPM.
U.S. Pat. No. 4,661,760, issued to Goto et al., discloses a control system for an engine-driven generator. The control system detects the current supplied to the electrical load and alters the generator output voltage level through field regulation in accordance with the detected current. The system is also capable of switching the generator output voltage level according to the state of the load applied, thereby improving power generation efficiency.
Conventional control systems having fixed hardware are unable to provide an adequate control of the alternator response to variations in current demand.